Osteoarthritis is characterized by the progressive loss of articular cartilage. Eventually, in many cases, the entirety of the articular cartilage in certain diarthrodial joints such as the knee, where the femur and tibia articulate, is lost.
Joint injury and osteoarthritis are major causes of lameness and disability. Mammals have pain that typically worsens with weight-bearing and activity and improves with rest. Inflammation may be mild and localized in the affected joint. Although the etiology of osteoarthritis remains unknown, biomechanical stresses and biochemical changes in the articular cartilage, subchondral bone and synovial membrane, as well as genetic factors, are all important in its pathogenesis. The synovial fluid's capacity to lubricate and to absorb impact is reduced in affected joints. These changes are due to a reduction in the size, concentration and quality of hyaluronan molecules naturally present in synovial fluid.
Commonly used treatments and medications only provide palliative care. Palliative care is defined as any form of medical care or treatment that concentrates on reducing the severity of disease symptoms, rather than halting or delaying progression of the disease or providing a cure. Non-Steroidal Anti-inflammatory Drugs (NSAIDs) are frequently prescribed or self-administered ad libitum. Types include aspirin, ibuprophen, acetaminophen, and naproxen. Although NSAIDs work well for their intended purpose, long-term use of these drugs can cause stomach problems such as ulcers and bleeding.
In April 2005, the FDA asked manufacturers of NSAIDs to include a warning label on their product to alert users of an increased risk for cardiovascular events (heart attacks and strokes) and gastrointestinal bleeding. Certain NSAIDs may also weaken bone and increase the risk of bone fractures.
COX-2 inhibitors (coxibs) are also used to treat symptoms. Coxibs block an inflammation-promoting enzyme called COX-2. This class of drugs was initially believed to work as well as traditional NSAIDs, but with fewer stomach problems. However, numerous reports of heart attacks and strokes have prompted the FDA to re-evaluate the risks and benefits of the COX-2s. Certain COX-2s have been withdrawn from the US market following reports of heart attacks in some patients taking the drugs. COX-2s still commercially available are labeled with strong warnings and a recommendation that it be prescribed at the lowest possible dose for the shortest duration possible. However, neither NSAIDs nor COX-2 inhibitors are known to stop or restore the loss of articular cartilage, which is the hallmark of osteoarthritis and the cause of the symptoms.
Steroids and artificial joint fluid (Synvisc, Hyalgan, etc.) can be injected directly into the joint capsule to reduce pain and inflammation for up to six months but have attendant injection site risks and do not improve the underlying cartilage condition.
Natural substances marketed in the United States as dietary supplements are also administered in cases of osteoarthritis. In particular, glucosamine, chondroitin sulfate, and methylsulfonylmethane (MSM) are administered in order to provide some relief from the symptoms of osteoarthritis. However, none of these substances is known to address cartilage loss, the root cause of osteoarthritis symptoms.
While exogenous hyaluronan has been administered via intraarticular and intravenous injections to mammals, it is not generally known that hyaluronan in an effective amount could be absorbed following perioral administration. Furthermore, there is no teaching in the art of a method for preventing, slowing, attenuating, mitigating, and/or ameliorating the loss of articular cartilage in osteoarthritis in a vertebrate subject, the method comprising the step of administering a composition comprising a therapeutically effective amount of an exogenous hyaluronan to the subject. The present disclosure provides such a method.